Year	mmol per litre
1980	5.756
1981	5.767
1982	5.775
1983	5.783
1984	5.792
1985	5.802
1986	5.811
1987	5.82
1988	5.826
1989	5.829
1990	5.83
1991	5.831
1992	5.83
1993	5.822
1994	5.811
1995	5.797
1996	5.778
1997	5.757
1998	5.733
1999	5.704
2000	5.67
2001	5.633
2002	5.594
2003	5.556
2004	5.515
2005	5.475
2006	5.437
2007	5.402
2008	5.368